The present invention relates to a method of processing a sample to find a cross section using a focused ion beam instrument.
A known method of finding a cross section of a sample using a focused ion beam instrument is disclosed, for example, in Japanese Patent Laid-Open No. 62-174918. That is, an ion beam is perpendicularly directed to a location on a sample surface where a cross section should be created, thus forming a vertical cross section. The cross section is observed.
One known method for obtaining a cross section which does not use a focused ion beam is to cleave a sample. Another known method not using a focused ion beam is to polish a sample. With either method, the target position to be processed cannot be precisely determined. On the other hand, with the method using a focused ion beam, the target processed position can be precisely determined and processed by combining a microscope function with a lithography function.
However, with the rapid development of more advanced semiconductor fabrication techniques and other techniques, the cross-sectional shape of the sample to be observed becomes increasingly finer. The thinnest laminated structure used in semiconductor devices recently developed is less than 10 nm. Therefore, where a vertical cross section is formed and scanned to observe the exposed surface, it is difficult to make the observation, because the resolution of the observing instrument is approached very closely. Furthermore, where the compositional analysis of the cross-sectional structure is performed, the irradiating energy beam can be focused less sharply than the energy beam of the observing instrument. Accordingly, analysis by the prior art method has become increasingly unfeasible.